The global prevalence and genetic spectrum of lysosomal acid lipase deficiency: A rare condition that mimics NAFLD

Clinical outcome of a patient with lysosomal acid lipase deficiency and first results after initiation of treatment with Sebelipase alfa: A case report

We report on a case of very rare autosomal recessive cholesteryl ester storage disease due to lysosomal acid lipase deficiency (LALD). LALD is caused by mutations in the lysosomal acid lipase A (LIPA) gene resulting in cholesteryl ester accumulation in liver, spleen, and macrophages. It can lead to liver failure, accelerated atherosclerosis and premature death. Until recently, treatment options were limited to lipid-lowering medications to control dyslipidemia. Presently, a long-term enzyme replacement therapy with Sebelipase alfa, a recombinant human lysosomal acid lipase, is available for patients with LALD. Our patient's condition became conspicuous at the age of two due to a xanthogranuloma of the chin together with increased lipid levels, elevated liver enzymes and hepatomegaly. It took another five years until our patient was diagnosed with LALD after genetic testing. A bi-weekly therapy with intravenous Sebelipase alfa was started at the age of 26 years. It led to normalization of lipid levels, reduction of liver enzymes and beginning regression of hepatomegaly in the absence of adverse drug reactions after 46 infusions. Since LALD can take a fatal course even in patients with a long-term stable condition, it is essential to identify affected patients early and to treat them appropriately by enzyme replacement therapy. LALD should be suspected in patients with low high-density lipoprotein cholesterol (HDL-C) and high low-density lipoprotein cholesterol (LDL-C) in conjunction with elevated liver enzymes or hepatomegaly. A registry for LALD patients shall help to advance our understanding of the disease as well as improve patient care (NCT01633489).

A kinetic assay of total lipase activity for detecting lysosomal acid lipase deficiency (LAL-D) and the molecular characterization of 18 LAL-D patients from Russia

Laboratory diagnostics of lysosomal acid lipase deficiency (LAL-D), a rare disorder associated with LIPA alterations, are based on the evaluation of LAL activity. In dry blood spots (DBS) submitted for LAL-D diagnostics (the screening cohort) over a two-year period or obtained from a cohort of retrospective LAL-D patients, we measured: (1) LAL activity using a two-reaction assay with 4-methylumbelliferone palmitate (4-MU-Palm) and Lalistat-2, a specific LAL inactivator; (2) total lipase (TL) activity by a 1-hour kinetic 4-MU-Palm cleavage reaction (no Lalistat-2). The TL activity was expressed as the area under the kinetic curve after 1 hour (TL-AUC1h) of the reaction and presented as the median (min-max). LAL activity was reduced in 30/537 individuals from the screening cohort, among which LIPA sequencing revealed six patients and one carrier. Overall, 16 (89%) individuals among six novel and 12 retrospective LAL-D patients carried at least one c.894G>A mutation (six were homozygous). The TL-AUC1h in nonLAL-D specimens with normal LAL activity (n = 90) was unambiguously higher (9471 [4015-23 585] RFU*h/punch) compared to LAL-D patients, including six new and nine retrospective patients (1810 [357-2608] RFU*h/punch). Importantly, in 13/15 examined nonLAL-D specimens with reduced LAL activity the TL-AUC1h was above a threshold of 2652 RFU*h/punch. Applying this threshold, the TL-AUC1h index discriminated all LAL-D patients (100% sensitivity) and 103/105 nonLAL-D specimens (98% specificity). Given that there is no need for Lalistat-2 and two parallel enzymatic reactions in conjunction with high sensitivity and specificity, the kinetic assay seems to be practical for LAL-D screening.

SYNOPSIS

Lysosomal acid lipase deficiency responsible for Wolman disease and cholesterol ester storage disease could be reliably detected using a kinetic assay of total lipase activity with a fluorogenic substrate.

Lysosomal acid lipase deficiency - early diagnosis is the key

Lysosomal acid lipase deficiency (LAL-D) is an ultra-rare lysosomal storage disease that may present from infancy to late adulthood depending on residual enzyme activity. While the severe form manifests as a rapidly progressive disease with near universal mortality within the first 6 months of life, milder forms frequently go undiagnosed for prolonged periods and typically present with progressive fatty liver disease, enlarged spleen, atherogenic dyslipidemia and premature atherosclerosis. The adult variant of LAL-D is typically diagnosed late or even overlooked due to the unspecific nature of the presenting symptoms, which are similar to common changes observed in the context of the metabolic syndrome. This review is aimed at delineating clinically useful scenarios in which pediatric or adult medicine clinicians should be aware of LAL-D as a differential diagnosis for selected patients. This is particularly relevant as a potentially life-saving enzyme replacement therapy has become available and the diagnosis can easily be ruled out or confirmed using a dried blood spot test.

Lysosomal Acid Lipase: From Cellular Lipid Handler to Immunometabolic Target

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl esters (CEs) and triglycerides (TGs) to free cholesterol (FC) and free fatty acids (FFAs), which are then used for metabolic purposes in the cell. The process also occurs in immune cells that adapt their metabolic machinery to cope with the different energetic requirements associated with cell activation, proliferation, and polarization. LAL deficiency (LALD) causes severe lipid accumulation and affects the immunometabolic signature in animal models. In humans, LAL deficiency is associated with a peculiar clinical immune phenotype, secondary hemophagocytic lymphohistiocytosis. These observations suggest that LAL might play an important role in cellular immunometabolic modulation, and availability of an effective enzyme replacement strategy makes LAL an attractive target to rewire the metabolic machinery of immune cells beyond its role in controlling cellular lipid metabolism.